Eutrophic Lake In China Research Articles

Exploring change of internal nutrients cycling in a shallow lake: A dynamic nutrient driven phytoplankton model

Lake eutrophication is associated with excessive nutrient enrichment and unobserved internal nutrient cycling. In spite of advances in understanding the role of nitrogen (N) and phosphorus (P) cycling in eutrophication, the relative importance of N and P limitation and release from sediment is still an open question. The complicated interaction between N and P cycling and external driving factors leads to dynamics in N or P limitation patterns and internal release that change over time. We developed a nutrient-driven model of phytoplankton dynamics including the critical nutrient cycling processes. It was fitted using Bayesian inference to explore the roles of N and P inputs from external sources, net sediment release, and internal dynamics in Lake Yilong, a shallow eutrophic lake in China. The model provided a good fit to observations, with time-varying parameters required to fit time-dependent variations in the sediment release process. The results demonstrated that, in Lake Yilong, the pattern of nutrient limitation showed a transformation from P limitation to N and P co-limitation after an observed regime shift occurred in 2008. After the shift in 2008, sediment release had an increasing influence on N and P supply, which could make eutrophication remediation more difficult. For Lake Yilong, it would not be possible to reverse eutrophication solely with watershed nutrient load reduction so in-lake manipulation of physical–chemical conditions to inhibit the sediments release should also be considered.

Estimation of nitrogen and phosphorus flows in livestock production in Dianchi Lake basin, China.

We assessed the nitrogen (N) and phosphorus (P) flows in intensified livestock production systems by investigating nutrient budgets and cycling in the basin of Dianchi Lake, one of the most eutrophic lakes in China. We conducted field surveys based on feed samplings and interviews of livestock farmers. The N and P in local and external feeds, animal body retentions, animal products and excretions were calculated at the individual level for dairy cattle, fattening pigs, breeding sows, broilers and laying hens. The N and P flows in the total livestock production system in the area were estimated by multiplying the individual N and P budgets by the number of animals. For the dairy and fattening pig productions, N and P supplied from local crops or by-products accounted for large parts of the inputs. For the other livestock categories, most of the N and P inputs depended on external resources. The N and P outputs through animal manure into the cropland were 287 and 66 kg/ha/year, respectively, which were higher than the N and P inputs into the livestock production systems from the cropland. The N and P loads from manure should be reduced for the establishment of sustainable agricultural production systems.

Comparative genomics reveals diversified CRISPR-Cas systems of globally distributed Microcystis aeruginosa, a freshwater bloom-forming cyanobacterium.

Microcystis aeruginosa is one of the most common and dominant bloom-forming cyanobacteria in freshwater lakes around the world. Microcystis cells can produce toxic secondary metabolites, such as microcystins, which are harmful to human health. Two M. aeruginosa strains were isolated from two highly eutrophic lakes in China and their genomes were sequenced. Comparative genomic analysis was performed with the 12 other available M. aeruginosa genomes and closely related unicellular cyanobacterium. Each genome of M. aeruginosa containing at least one clustered regularly interspaced short palindromic repeat (CRISPR) locus and total 71 loci were identified, suggesting it is ubiquitous in M. aeruginosa genomes. In addition to the previously reported subtype I-D cas gene sets, three CAS subtypes I-A, III-A and III-B were identified and characterized in this study. Seven types of CRISPR direct repeat have close association with CAS subtype, confirming that different and specific secondary structures of CRISPR repeats are important for the recognition, binding and process of corresponding cas gene sets. Homology search of the CRISPR spacer sequences provides a history of not only resistance to bacteriophages and plasmids known to be associated with M. aeruginosa, but also the ability to target much more exogenous genetic material in the natural environment. These adaptive and heritable defense mechanisms play a vital role in keeping genomic stability and self-maintenance by restriction of horizontal gene transfer. Maintaining genomic stability and modulating genomic plasticity are both important evolutionary strategies for M. aeruginosa in adaptation and survival in various habitats.

Dynamics of chromophoric dissolved organic matter influenced by hydrological conditions in a large, shallow, and eutrophic lake in China.

High concentrations of chromophoric dissolved organic matter (CDOM) are terrestrially derived from upstream tributaries to Lake Taihu, China, and are influenced by hydrological conditions of the upstream watershed. To investigate how the dynamics of CDOM in Lake Taihu are influenced by upstream inflow runoff, four sampling cruises, differing in hydrological conditions, were undertaken in the lake and its three major tributaries, rivers Yincun, Dapu, and Changdou. CDOM absorption, fluorescence spectroscopy, chemical oxygen demand (COD), and stable isotope δ(13)C and δ(15)N measurements were conducted to characterize the dynamics of CDOM. The mean absorption coefficient a(350) collected from the three river profiles (5.15 ± 1.92m(-1)) was significantly higher than that of the lake (2.95 ± 1.88m(-1)), indicating that the upstream rivers carried a substantial load of CDOM to the lake. This finding was substantiated by the exclusively terrestrial signal exhibited by the level of δ(13)C (-26.23 ± 0.49‰) of CDOM samples collected from the rivers. Mean a(350) and COD in Lake Taihu were significantly higher in the wet season than in the dry season (t test, p < 0.0001), suggesting that the abundance of CDOM in the lake is strongly influenced by hydrological conditions of the watershed. Four components were identified by parallel factor analysis, including two protein-like components (C1 and C2), a terrestrial humic-like component (C3), and a microbial humic-like (C4) component. The contribution percentage of the two humic-like components relative to the summed fluorescence intensity of the four components (C humic) increased significantly from the dry to the wet season. This seasonal difference in contribution further substantiated that an enhanced rainfall followed by an elevated inflow runoff in the lake watershed in the wet season may result in an increase in humic-like substances being discharged into the lake compared to that in the dry season. This finding was further supported by an elevated a(250)/a(365) of CDOM samples collected in the lake in the wet season than in the dry season. Significantly higher mean levels of C3 and a(350) were recorded for CDOM samples collected from River Yincun than those from rivers Dapu and Changdou, differing in seasons, suggesting the significance of terrestrial CDOM input from River Yincun.

Effects of wind wave turbulence on the phytoplankton community composition in large, shallow Lake Taihu.

Wind waves are responsible for some of the spatio-temporal gradients observed in the biotic and abiotic variables in large shallow lakes. However, their effects on the phytoplankton community composition are still largely unexplored especially in freshwater systems such as lakes. In this paper, using field observations and mesocosm bioassay experiments, we investigated the impact of turbulence generated by wind waves on the phytoplankton community composition (especially on harmful cyanobacteria) in Lake Taihu, a large, shallow eutrophic lake in China. The composition of the phytoplankton community varied with the intensity of wind waves in the different areas of the lake. During summer, when wind waves were strong in the central lake, diatoms and green algae seemed to dominate while harmful cyanobacteria dominated in the weakly influenced Meiliang Bay. Turbulence bioassays also showed that diatoms and green algae were favoured by turbulent mixing. The critical time for the shift of the phytoplankton community composition was approximately 10 days under turbulent conditions. However, short-term (6 days) turbulence is rather beneficial for the dominance of cyanobacteria. This study suggests that the duration of wind events and their associated hydrodynamics are key factors to understanding the temporal and spatial changes of phytoplankton communities.

Integrated SWAT model and statistical downscaling for estimating streamflow response to climate change in the Lake Dianchi watershed, China

Understanding the relationships between hydrological regime and climate change is important for water resources management. In this study, the streamflow response to climate change was investigated in the Lake Dianchi watershed, which is one of the most important eutrophic lakes in China. Daily time-series of temperature and precipitation in the future periods (2020, 2050 and 2080s) were projected from HadCM3 model. Statistical downscaling model (SDSM) and the previously calibrated and validated Soil and water assessment tool (SWAT) model were used to quantify the impacts of climate change on streamflow in this watershed. The results showed that SDSM can well capture the statistical relationships between the large scale climate variables and the observed weather at regional scale. The downscaled results showed that annual average maximum and minimum temperature would rise by 4.28 (3.25) and 4.71 °C (3.33 °C) in the 2080s under A2 (B2) scenario. Annual average precipitation would decrease within the range between 20.34 and 74.12 mm under both scenarios in the future. Based on SWAT model simulation, annual average streamflow would decrease in the future by the declination of −7.12 to −21.83 % and −6.34 to −17.09 % under A2 (B2) scenarios in the outlet of this watershed. The frequency of drought and extreme rainfall events would increase in the future, which is not beneficial to protect Lake Dianchi. This study could lead to a better understanding of the streamflow response under climate change and also raised concerns about the sustainability of future water resources in Lake Dianchi watershed.

Reliability-oriented multi-objective optimal decision-making approach for uncertainty-based watershed load reduction

Water quality management and load reduction are subject to inherent uncertainties in watershed systems and competing decision objectives. Therefore, optimal decision-making modeling in watershed load reduction is suffering due to the following challenges: (a) it is difficult to obtain absolutely “optimal” solutions, and (b) decision schemes may be vulnerable to failure. The probability that solutions are feasible under uncertainties is defined as reliability. A reliability-oriented multi-objective (ROMO) decision-making approach was proposed in this study for optimal decision making with stochastic parameters and multiple decision reliability objectives. Lake Dianchi, one of the three most eutrophic lakes in China, was examined as a case study for optimal watershed nutrient load reduction to restore lake water quality. This study aimed to maximize reliability levels from considerations of cost and load reductions. The Pareto solutions of the ROMO optimization model were generated with the multi-objective evolutionary algorithm, demonstrating schemes representing different biases towards reliability. The Pareto fronts of six maximum allowable emission (MAE) scenarios were obtained, which indicated that decisions may be unreliable under unpractical load reduction requirements. A decision scheme identification process was conducted using the back propagation neural network (BPNN) method to provide a shortcut for identifying schemes at specific reliability levels for decision makers. The model results indicated that the ROMO approach can offer decision makers great insights into reliability tradeoffs and can thus help them to avoid ineffective decisions.

Responses of chlorophyll and MDA of Vallisneria natans to nitrogen and phosphorus availability and epiphytic algae

It is common for submerged plants to become less abundant and disappear in eutrophic lakes in the world. To explore degradation mechanisms of submerged plants during the growing season, we determined chlorophyll and malondialdehyde (MDA) concentrations in Vallisneria natans (Lour.) Hara cultivated under four different nutrient concentrations (N/P, mg/L): T1 = 0.5/0.05, T2 = 2.5/0.25, T3 = 4.5/0.45, and T4 = 12.5/1.25) and under low and high density of epiphytic algae. With the increase in nutrients, the content of chlorophyll in the leaves of V. natans varied in the order T3 > T2 > T1 (T4) at low density (grazed) of epiphytic algae and varied in the order T3 > T2 > T1 > T4 in the high density (ungrazed) of epiphytic algae. With the increase in nutrients, the content of MDA in the leaves of V. natans varied in the order T4 >T1 (T2, T3) at the low density (grazed) of epiphytic algae and varied as T4 > T3 > T2 > T1 at the high density of epiphytic algae. At the same time, chlorophyll content of V. natans was significantly higher (p < 0.01 and the content of MDA was significantly lower (p < 0.01) in the grazed treatment than in the non-grazed treatment under the same nutrient concentrations. During the growing season, total nitrogen and total phosphorus concentrations were low (N < 4.5 mg N/L, P < 0.45 mg P/L) in Lake Taihu, a large shallow eutrophic lake in China; consequently water column nutrient loading benefited the growth of V. natans, but the high biomass of epiphytic algae and planktonic algae caused by the high nutrient loading of water column inhibited the growth of V. natans.

Speciation of organic phosphorus in a sediment profile of Lake Taihu I: Chemical forms and their transformation

Organic phosphorus (nonreactive P, NRP) is a major component of P in sediments, but information about its chemical forms and dynamic transformation is limited. The chemical forms and dynamic behaviors of NRP in a sediment profile from Lake Taihu, a freshwater and eutrophic lake in China, were investigated. Five forms of NRP in the sediments were extracted based on a chemical fractionation technique, including easily labile NRP (NaHCO3-NRP), reactive metal oxide-bound NRP (HC1-NRP), humic acid-associated NRP (NaOH-NRPHA), fulvic acid-associated NRP (NaOH-NRPFA) and residual NRP (Res-TP). There were notable transformations with increasing sediment depth from the labile NaHCO3-NRP and NaOH-NRP pools to the recalcitrant HC1-NRP and Res-TP pools, which caused the NRP to become increasingly recalcitrant as the early diagenetic processes proceeded. Further analyses showed that the relative changes in contents of organic matter and reactive Fe oxides in the sediment profile triggered a competition for binding NRP fractions and led to the transformation of NRP. The results highlighted the importance of abiotic processes in regulating the diagenesis of organic P and its stability in sediments.

Risk assessment of microcystins in silver carp (Hypophthalmichthys molitrix) from eight eutrophic lakes in China

Bioaccumulation and risk assessment of microcystins (MCs) in muscle of silver carp (Hypophthalmichthys molitrix) from eight eutrophic lakes along the Yangtze River of China were examined by using liquid chromatography electrospray ionisation mass spectrometry. MCs contents in seston collected from these eutrophic lakes ranged from 0.02 to 21.7μg/L. MCs concentrations in silver carp muscle samples varied from 0.014 to 0.036μg/gDW with an average of 0.028μg/gDW. The total length of silver carp showed a significant negative correlation with MCs concentrations in their muscle (r=−0.85, p<0.05), suggesting that MCs accumulation in silver carp muscle seems to be size dependent. EDI values of MCs in fish muscle from these eight eutrophic lakes varied from 0.0027 to 0.0071μg/kgday, which was much lower than the TDI value of 0.04μg/kgday previously established by WHO, indicating that it is safe to consume silver carp muscle from eutrophic lakes in China.

The spatio-temporal variations of sedimentary phosphorus in Taihu Lake and the implications for internal loading change and recent eutrophication

Internal phosphorus loading is particularly concerned for the shallow lakes due to the frequent sediment disturbance, which may play a vital role in changing nutrient level in overlying water. A historical perspective on internal phosphorus loading may contribute to understanding its contribution to recent eutrophication. In this work, a study on the changes in internal phosphorus loading and release potential in Taihu Lake, a shallow eutrophic lake in China, was performed based on the analysis of spatio-temporal variations of sedimentary total phosphorus and three operationally defined fractions (NaOH-P, HCl-P and OP). The influencing factors for changing internal loading were discussed. The results showed that internal phosphorus loading was elevated compared to pre-eutrophication periods and the increase has occurred since approximately the late 1970s to early 1980s. Changes in internal phosphorus loading were primarily attributed to the NaOH-P and OP fractions, relating to anthropogenic inputs and enhanced productivity, respectively. The internal phosphorus release potential may be enhanced by up to 22% currently relative to the pre-eutrophication period; however, it should play a secondary role to external input in enhancing nutrient levels and sustaining the eutrophication in Taihu Lake.

Shifts between ammonia-oxidizing bacteria and archaea in relation to nitrification potential across trophic gradients in two large Chinese lakes (Lake Taihu and Lake Chaohu)

Ammonia oxidation plays a pivotal role in the cycling and removal of nitrogen in aquatic ecosystems. Recent findings have expanded the known ammonia-oxidizing prokaryotes from Bacteria to Archaea. However, the relative importance of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in nitrification is still debated. Here we showed that, in two large eutrophic lakes in China (Lake Taihu and Lake Chaohu), the abundance of AOA and AOB varied in opposite patterns according to the trophic state, although both AOA and AOB were abundant. In detail, from mesotrophic to eutrophic sites, the AOA abundance decreased, while the AOB increased in abundance and outnumbered the AOA at hypertrophic sites. In parallel, the nitrification rate increased along these trophic gradients and was significantly correlated with both the AOB abundance and the numerical ratio of AOB to AOA. Phylogenetic analysis of bacterial amoA sequences showed that Nitrosomonas oligotropha- and Nitrosospira-affiliated AOB dominated in both lakes, while Nitrosomonas communis-related AOB were only detected at the eutrophic sites. The diversity of AOB increased from mesotrophic to eutrophic sites and was positively correlated with the nitrification rate. Overall, this study enhances our understanding of the ecology of ammonia-oxidizing prokaryotes by elucidating conditions that AOB may numerically predominated over AOA, and indicated that AOA may play a less important role than AOB in the nitrification process of eutrophic lakes.

Species‐dependent effects of crustacean plankton on a microbial community, assessed using an enclosure experiment in Lake Taihu, China

A mesocosm experiment was performed to evaluate the species‐dependent effects of crustacean plankton on the microbial community in Lake Taihu, a large shallow eutrophic lake in China. Four dominant species of crustacean plankton (Daphnia galeata, Bosmina longirostris, Neodiaptomus schmackeri, and Mesocyclops dissimilis) in Lake Taihu were selected as predators. Denaturing gradient gel electrophoresis and cloning and sequencing of polymerase chain reaction–amplified ribosomal ribonucleic acid gene fragments were applied to analyze the microbial eukaryotic community composition (MECC) and bacterial community composition (BCC). The changes in the abundance of bacteria, heterotrophic nanoflagellates, ciliates, and phytoplankton were also measured. Crustacean plankton had a significant effect on phytoplankton biomass, the abundance of ciliates and bacteria, and the percentage of filamentous bacteria among total bacteria. Nonmetric multidimensional scaling analysis showed that the MECC and BCC in the treatments involving the same species were generally more similar to each other than to those in treatments with other species on both days 7 and 15. The MECC were clustered into two distinct groups between the cladoceran and copepod treatments on days 7 and 15. A phylogenetic analysis revealed that alveolates, chlorophytes, and fungi were the most important groups in the microbial eukaryotic clone libraries. Crustacean plankton had a significant species‐dependent effect on the microbial eukaryotic community and might have both trophic and nontrophic effects on the bacterial community.

Initial identification of heavy metals contamination in Taihu Lake, a eutrophic lake in China

A detailed investigation of seven heavy metals (Cu, Cd, Cr, As, Pb, Zn, Ni) in the water column, interstitial water and surface sediment was conducted to quantify the extent of their contamination in Taihu Lake. Results showed the average total concentrations ranged from 0.93 μg/L for Cd to 47.03 μg/L for Zn. The dissolved concentrations in the overlying water ranged from 0.06 μg/L for Cd to 15.86 μg/L for Zn. The metals in the Taihu Lake surface water were primarily in the particulate phase, especially for Cd, whose particulate concentration represented 94.3% of the total. In the surface sediment, the mean concentrations for Cr, Ni, Cu, Zn, As, Cd and Pb were 41.50, 28.72, 27.82, 65.46, 5.94, 0.82 and 41.17 mg/kg, respectively. The metals in the water column and sediments of Taihu Lake displayed significant spatial variations, and the higher metal concentrations mainly occurred in the north and west of Taihu Lake, especially in Zhushan Bay and West Taihu Lake. A quality assessment indicated that most of the metals in the surface water of Taihu Lake had no or low adverse health effects on organisms, except for Pb and Cu, which may cause chronic toxicity. Compared with the “Consensus-Based Sediment Quality Guidelines”, the polluting metals were Cr, Ni and Cd, and the polluted regions were confined to Zhushan Bay, Meiliang Bay and the west of Taihu Lake, especially for north of Zhushan Bay. The polluted areas for Cr, Ni and Cd were 14.36, 34.70 and 13.24 km2, respectively. We suggest that Cr, Ni, and Cd in the polluted areas should be addressed and that tissue chemistry and sediment toxicity assessments be performed as soon as possible.

Environmental and economic analysis of application of water hyacinth for eutrophic water treatment coupled with biogas production

The proliferation of water hyacinth is currently controlled by removing it from a water body and disposing it by landfill in China. Using water hyacinth to remove nutrients from water bodies and to produce biogas is another technically feasible option for the control of water hyacinth, but its environmental and economic performances are not well understood. This study collected data from an experimental biogas plant to develop a lifecycle analysis and a cost benefit analysis for the control of water hyacinth proliferation in a eutrophic lake in China. Comparison was made between the alternative option of using water hyacinth for biogas production and the current practice of disposing it in landfills. The results reveal that the biogas option is economically feasible with a positive energy balance. The removal of water hyacinth to produce biogas can contribute to water quality improvement and GHG emission reduction whose values, however, depend on the processing scale of the biogas plant. Since both the current approach and the biogas option can remove nutrients from water bodies, the additional value of water quality improvement resulting from the biogas option is only possible when the processing scale of the biogas plant is greater than the amount of water hyacinth disposed by landfill. The emission of methane deserves attention when water hyacinth is disposed by landfill. The biogas option can respond to China's policies on water pollution control, renewable energy development, and energy saving and emission reduction.

Compositional differences among planktonic ciliate communities in four subtropical eutrophic lakes in China

Ciliate community composition was investigated in four subtropical eutrophic lakes with cyanobacterial blooms in three seasons during 2009–2010 using the quantitative protargol staining approach. Among the four lakes, Lake Taihu and Chaohu are situated in the mid-lower Yangtze Plain near sea level, and Lake Dianchi and Xingyunhu are located on the Yunnan–Kweichow Plateau. A total of 102 ciliate species, representing 15 orders and 66 genera, were studied. Ciliate communities in Lake Taihu and Chaohu were characterized by abundant algivorous and mixotrophic oligotrichs and prostomatids, while Lake Dianchi and Xingyunhu ciliate communities were primarily characterized by voracious bacterivorous scuticociliates and peritrichids. Cluster analysis based on the transformed square root of ciliate abundance showed that samples from Lake Taihu and Chaohu composed one group whereas samples from Lake Dianchi and Xingyunhu composed another group in each season. Our results indicated that all dominant ciliate species are ubiquitous and that species dominance is regulated by different factors in different subtropical eutrophic lakes.

Distribution and Fractions of Phosphorus and Nitrogen in Surface Sediments from Dianchi Lake, China

Dianchi Lake is one of the most three seriously eutrophic lakes in China. In the present study, the phosphorus (P) and nitrogen (N) fractions in 37 surface sediments samples collected in the Dianchi Lake were investigated. The total phophorus (TP) in sediments was divided into two parts: inorganic P (IP) and residual P (Res-P). The results showed that the total phosphorus content in surface sediments ranged from 1465.27 to 3650.12 mg/kg, IP was the major component of TP and the Ca bound P was the main fraction of IP. The bio-available phosphorus (BAP) in Dianchi Lake was first estimated in this study. BAP ranged from 215.66 to 678.02 mg/kgand the mean concentration was 382.78±89.77 mg/kgfor all 37 samples. The nitrogen fractions for the whole Dianchi Lake were firstly studied. It was shown that the sediment had been an important N nutrient source of the water, owing to the high content of transferable nitrogen forms in the sediment.

Profundal oligochaete assemblages in Palaearctic lakes

The profundal oligochaete fauna is mostly formed of species present also in shallower waters. Endemic taxa have developed only in ancient rift lakes like Lake Baikal. "Common" lakes, mostly of glacial or volcanic origin, are too ephemeral for speciation. In the profundal of larger European oligotrophic lakes, there can occur about 10 tubificid and lumbriculid species. With a decline in dissolved oxygen in water, only 1-2 of them will remain, Tubifex tubifex often being the last survivor. In eutrophic lakes, Potamothrix hammoniensis is the climax species. In the Far East, the profundal is also inhabited by a small assortment of oligochaetes from surrounding waters. In the eutrophic lakes of Honshu (Japan), the widely distributed species Limnodrilus hoffmeisteri and T. tubifex dominate, while more species occur in the northern oligotrophic lakes. In the eutrophic lakes in China, L. hoffmeisteri or Branchiura sowerbyi dominates. The zoogeographical origin of the commonest profundal oligochaetes is discussed.

Using sediment seed banks and historical vegetation change data to develop restoration criteria for a eutrophic lake in China

Restoration of submerged macrophytes to lake that have lost them can be difficult but can be helped by studies on historical vegetation data and remnant seed banks in the sediments. We analysed sediment seed banks and historical vegetation change data in Lake Dianchi, China, and aimed to develop a possible recovery trajectory of submerged vegetation. The results indicate that phosphorus concentrations have increased by 28 times in the lake since 1961 and macrophytes that used to grow at 5–6.5 m are now confined to water less than 3 m deep. Many species had disappeared by 1978 and a former 17 species and 88% cover in 1961 was reduced to 9 species in three turbidity-tolerant communities with only 2% cover by 2010. The remaining seed bank was dominated by two species, still present in the lake and many former species, which had been very abundant, were not found as seeds. We suggest that macrophytes can be restored to areas shallower than 3 m by using three turbidity-tolerant species, and that other formerly present species will need to be reintroduced when conditions have been further improved.

Food web structure of a shallow eutrophic lake (Lake Taihu, China) assessed by stable isotope analysis

Lake Taihu is a large, shallow, and eutrophic lake in China. It has provided local communities with valuable fisheries for centuries, but little is known of the trophodynamics, or of its faunal communities. Carbon and nitrogen isotopic composition was used to assess its trophic pathways and the food web structure [food sources and trophic levels (TL)]. Basal food sources were distinguishable based on their δ13C values, ranging from −27.2 to −15.2‰. Consumers were also well separated in δ13C (−26.9 to −17.9‰ for invertebrates and −25.7 to −18.1‰ for fishes), which allowed for an effective discrimination of carbon sources between these fauna. An average trophic enrichment factor of 3.4‰ was used to calculate the TLs based on δ15N of zooplankton, with results indicating a food web having four TLs. Although δ15N values overlap and cover a large range within trophic compartments, the isotopic signatures of the species assessed revealed a general trend of 15N enrichment with increasing TL. Stable isotope signatures were also used to establish a general food web scheme in which five main trophic pathways were analyzed.